For a storage device, a technique of a redundant array of inexpensive disks (RAID) is used in which performance and failure tolerance is ensured by distributing data to multiple hard disks (magnetic disk devices). The storage device uses a RAID controller to achieve the technique of RAID such as arrangement of data in the disks, securement of redundancy (duplication) of the data.
In a disk device, adjacent track interference (ATI) may occur due to a high recording density. When the ATI occurs, writing of data into a certain sector may cause deletion of data stored in a data sector in an adjacent track due to leaking of a magnetic field for writing.
The disk device scans storage regions of the disk device in order to diagnose data affected by the ATI. If the data affected by the ATI is detected and to be recovered, the disk device rewrites the data affected by the ATI. As techniques for handling the ATI, there are the following techniques, for example.
As the first technique, there is a medium scanning method for causing a disk device to execute a process of writing information transmitted by a host device in a storage medium in response to a request from the host device. The medium scanning method causes the disk device to execute a medium monitoring process, a medium scanning determination process, and a medium scanning process. In the medium monitoring process, the disk device monitors the state of the storage medium in which the information has been written in the writing process. In the medium scanning determination process, the disk device determines, on the basis of the state of the storage medium, whether or not the storage medium is to be scanned. In the medium scanning process, the disk device scans the storage medium determined to be scanned in the medium scanning determination process.
As the second technique, there is a technique for efficiently inhibiting execution of unwanted refreshing. For the second technique, a magnetic disk device includes a grouping section and a refreshing controller. The grouping section classifies a group of tracks located on a disk into multiple groups each having multiple tracks including two or more tracks of which physical positions are not continuous. The refreshing controller controls, on a group basis, a refreshing process to be executed on the multiple groups.
As the third technique, there is an error state processing method for processing an error state of a large-capacity data storage device configured to store data on concentrically adjacent tracks of an electromagnetic storage medium. The error state processing method includes a process of detecting a state in which a track squeeze error is likely to occur during access to a specific region within the storage medium and a process of rewriting data on at least one track located closest to the specific region.
Related techniques are disclosed in, for example, Japanese Laid-open Patent Publication No. 2007-242207, Japanese Laid-open Patent Publication No. 2012-14790, and Japanese Laid-open Patent Publication No. 2005-322399.
If degraded data is detected as a result of scanning for diagnosing data affected by the ATI and degraded, and if the data is determined to be recovered, the disk device executes a process (data refreshing) of rewriting data. During the process, the disk device does not execute an input and output (I/O) process.
Thus, when the disk devices included in the storage device individually execute the scanning and the data refreshing, the I/O process may be delayed by the number of the disk devices. It is, therefore, desirable that the scanning is to be executed by the disk devices at the same time and the data refreshing is to be executed by the disk devices at the same time.